Underground formation containing groundwater is called

aquifer

Explanation:

Most aquifers contain water saturated layers of rock or loose sediment. Aquifers have within them water- filled caves.

developed and developing countriescountries are divided into two major categories by the united nations, which are developed countries and developing countries. the classification of countries is based on the economic status such as gdp, gnp, per capita income, industrialization, the standard of living, etc. developed countries refers to the soverign state, whose economy has highly progressed and possesses great technological infrastructure, as compared to other nations.

c, this answer is productivity.